1. Field of the Invention
The present invention relates to a slide rail comprising a first member and a second member that are assembled to be slidable with respect to each other. More particularly, the present invention relates to a slide rail suitable for slidably connecting a main body and an image forming unit in an image forming apparatus, and the image forming apparatus.
2. Description of Related Art
In various types of apparatuses, heretofore, one or some of components thereof are mounted to be slidable with respect to a main body of each apparatus. This configuration is intended for example to facilitate replacement and maintenance of those components. In this case, the components are combined into a unit which can be pulled out from the main body. This unitized component is set to be slidably moved between a position for actual operation inside the main body and the other position for maintenance outside the main body. For this end, a slide rail is used. Such a configuration is applied to for example some image forming apparatus (JP2005-37677A).
For storage containers or the like, it is necessary to take a stored position and a pull-out position from the viewpoint of an intended purpose thereof besides maintenance. In such a component also, a container part is slidable with respect to a housing part and thus a slide rail is used (JP2002-17486A). Moreover, differently from the stored position and the pull-out position, there is also a component needing its positional adjustment to suit to the size of each user's body. One example thereof is a car seat using a slide rail (JP2010-100077A).
A slide rail usually consists of a long outer rail and a long inner rail slidably combined into one. The outer rail and the inner rail are fixed to different ones of two members to thereby assemble the two members slidably with respect to each other. FIGS. 10 to 12 show the shape of one end of an inner rail of a typical conventional slide rail. Specifically, FIGS. 10 and 11 are perspective views, showing each other's reverse sides and FIG. 12 is a plan view. An inner rail 70 shown in those figures is made from a long flat plate into such an illustrated shape. In this inner rail 70, an end portion 71 and a main portion 72 are different in shape.
The end portion 71 of the inner rail 70 consists of a part of a flat portion 73 and end-portion side walls 74 arranged on both sides of the flat portion 73. Each of the end-portion side walls 74 is made by bending a part of the original flat plate almost perpendicularly to and on the same side of the flat portion 73. On the other hand, the main portion 72 of the inner rail 70 also consists of the other part of the flat portion 73 and main-portion side walls 75 arranged on both sides of the flat portion 73. The flat portion 73 is continuous over the end portion 71 and the main portion 72. As with the end-portion side walls 74, each of the main-portion side walls 75 is also made by bending a part of the original flat plate on the same side of the flat portion 73. However, each main-portion side walls 75 is further bent at two different positions above the bent portion from the flat portion 73. Accordingly, each main-portion side wall 75 has a crank-like shape in cross-section defined by a lower wall portion 76, a middle step portion 77, and an upper wall portion 78.
Herein, relative to the flat portion 73, a protruding height H of each end-portion side wall 74 is larger than a protruding height H2 of each lower wall portion 76. Further, on each side of the flat portion 73, a slit 79 is formed between the end-portion side wall 74 and the main-portion side wall 75, so that the slit 79 completely separates the end-portion side wall 74 and the main-portion side wall 75. The slit 79 also extends slightly into the flat portion 73. This inner rail 70 is slidably inserted in an outer rail having a little larger cross-sectional shape than and a long length as with the inner rail 70, thus completing a slide rail. The outer rail is provided with a part that does not interfere with the main-portion side walls 75 but does interfere with the end-portion side walls 74. By contact of such part with the end-portion side walls 74, a slidable range of the inner rail 70 is limited. This allows the two members to slide but prevents from coming apart.
However, the aforementioned conventional slide rail has the following problems. To be concrete, the end-portion side walls 74 are low in strength, even though the end-portion side walls 74 have a function of limiting the slidable range by contacting a part of the outer rail as mentioned above. Accordingly, the end-portion side walls 74 bump on the relevant part of the outer rail with a considerably high frequency, resulting in deformation of the end-portion side walls 74. Thus, the end-portion side walls 74 lose the function of limiting the slidable range. The inner rail 70 is therefore liable to come off the outer rail. In other words, the conventional slide rail is poor in durability. Especially, this tendency is extreme in a case where a movable one of the two components is heavy. Also, there is a type using a ball bearing but it needs a large number of components, leading to a complex structure.